One of the most important requirements of a next generation wireless access system is to be able to support high data transmission rate. To this end, a variety of technologies including multiple input multiple output (MIMO), cooperative multipoint transmission (CoMP), and relays have been studied.
A legacy wireless access system has mainly considered only one carrier even though uplink bandwidth and downlink bandwidth are differently configured. For example, a wireless communication system in which one carrier is used for uplink and one carrier is used for downlink are one and bandwidth of uplink is generally symmetrical to bandwidth of downlink, based on a single carrier, has been provided.
Nonetheless, in consideration of saturated frequency resources, carrier aggregation (CA)/multiple cells for designing each of dispersed bandwidths to satisfy basic requirements capable of operating an independent system and for aggregating a plurality of bandwidths to one system has been introduced as a method for securing broad bandwidth in order to meet requirements for higher data transmission rate.
In this case, a carrier of a bandwidth unit available for an independent operation may be referred to as a component carrier (CC). To support increased transmission capacity, the bandwidth of a CC is extended to 20 MHz or more in a recent 3GPP long-term evolution-advanced (LTE-A) or 802.16m system. At this time, a broad bandwidth is supported by aggregating one or more CCs. For instance, if one CC supports a bandwidth of 5 MHz, 10 MHz, or 20 MHz, system bandwidth up to 100 MHz may be supported by aggregating a maximum of five CCs.